1 files changed, 73 insertions, 0 deletions
diff --git a/packages/integrations/markdoc/src/heading-ids.ts b/packages/integrations/markdoc/src/heading-ids.ts
new file mode 100644
index 000000000..57b84d059
--- /dev/null
+++ b/packages/integrations/markdoc/src/heading-ids.ts
@@ -0,0 +1,73 @@
+import Markdoc, { type ConfigType, type RenderableTreeNode, type Schema } from '@markdoc/markdoc';
+import Slugger from 'github-slugger';
+import { getTextContent } from './runtime.js';
+import type { AstroMarkdocConfig } from './config.js';
+import { MarkdocError } from './utils.js';
+
+function getSlug(
+	attributes: Record<string, any>,
+	children: RenderableTreeNode[],
+	headingSlugger: Slugger
+): string {
+	if (attributes.id && typeof attributes.id === 'string') {
+		return attributes.id;
+	}
+	const textContent = attributes.content ?? getTextContent(children);
+	let slug = headingSlugger.slug(textContent);
+
+	if (slug.endsWith('-')) slug = slug.slice(0, -1);
+	return slug;
+}
+
+type HeadingIdConfig = AstroMarkdocConfig<{
+	headingSlugger: Slugger;
+}>;
+
+/*
+	Expose standalone node for users to import in their config.
+	Allows users to apply a custom `render: AstroComponent`
+	and spread our default heading attributes.
+*/
+export const heading: Schema = {
+	children: ['inline'],
+	attributes: {
+		id: { type: String },
+		level: { type: Number, required: true, default: 1 },
+	},
+	transform(node, config: HeadingIdConfig) {
+		const { level, ...attributes } = node.transformAttributes(config);
+		const children = node.transformChildren(config);
+
+		if (!config.ctx?.headingSlugger) {
+			throw new MarkdocError({
+				message:
+					'Unexpected problem adding heading IDs to Markdoc file. Did you modify the `ctx.headingSlugger` property in your Markdoc config?',
+			});
+		}
+		const slug = getSlug(attributes, children, config.ctx.headingSlugger);
+
+		const render = config.nodes?.heading?.render ?? `h${level}`;
+		const tagProps =
+			// For components, pass down `level` as a prop,
+			// alongside `__collectHeading` for our `headings` collector.
+			// Avoid accidentally rendering `level` as an HTML attribute otherwise!
+			typeof render === 'function'
+				? { ...attributes, id: slug, __collectHeading: true, level }
+				: { ...attributes, id: slug };
+
+		return new Markdoc.Tag(render, tagProps, children);
+	},
+};
+
+// Called internally to ensure `ctx` is generated per-file, instead of per-build.
+export function setupHeadingConfig(): HeadingIdConfig {
+	const headingSlugger = new Slugger();
+	return {
+		ctx: {
+			headingSlugger,
+		},
+		nodes: {
+			heading,
+		},
+	};
+}